1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a semiconductor device having a nitride-based semiconductor field effect transistor structure and a method of manufacturing the same.
2. Description of the Related Art
In general, a group III-nitride-based semiconductor including group III elements such as gallium (Ga), aluminum (Al), indium (In), and the like, and nitrogen (N), has characteristics such as a wide energy band gap, high electron mobility, high saturation electron speed, high thermochemical stability, and the like. A nitride-based field effect transistor (N-FET) based on the group III-nitride-based semiconductor is manufactured using a semiconductor material having a wide energy band gap, for example, gallium nitride (GaN), aluminum gallium nitride (AlGaN), indium gallium nitride (InGaN), aluminum indium gallium nitride (AlInGaN), or the like.
A general N-FET has a High Electron Mobility Transistor (HEMT) structure. For example, a semiconductor device having the HMET structure includes a base substrate, a nitride-based semiconductor layer formed on the base substrate, and a source electrode and a drain electrode formed on the semiconductor layer, and a gate electrode formed on the semiconductor layer between the source electrode and the drain electrode.
According to such a semiconductor device, 2-Dimensional Electron Gas (2DEG), used as a current flow path, may be generated inside the semiconductor layer. The N-FET having the above-described structure has conventionally tried to enhance internal pressure and current density at the same time by adjusting a mixing ratio of aluminum (Al) and gallium nitride (GaN) in the epitaxial growth of aluminum gallium nitride (AlGaN). However, this is related to the epitaxial growth, rather than the change of the HEMT structure. Also, there has been an attempt to increase internal pressure by forming a Schottky electrode instead of an ohmic electrode at the time of forming the drain electrode. However, the Schottky contact results in a turn-on voltage between the drain electrode and the source electrode, thereby causing a reduction in the efficiency of the semiconductor device.